There’s never been a better time to be an enormous dork who loves puzzles. Late-2010s television has been dominated by the puzzle box, a narrative form that centers on unpacking a central mystery, exemplified in zeitgeist-capturing shows like Westworld, Russian Doll, and The Good Place. With carefully paced episodes that drop leading clues and execute disorienting plot twists, the format is optimized to capture and keep viewers’ curiosity.

Why are there so many puzzle box series at the moment, and why does their success keep compounding upon itself? One basic explanation is the explosion of TV: In 2018, 495 original television series aired in the U.S., compared with only 182 in 2002. But even within this overall growth, the number and variety of puzzle-box shows has expanded disproportionately. They air on primetime networks (Manifest), premium cable (The Leftovers, Twin Peaks: The Return), and streaming channels (Russian Doll, Homecoming). Their stories stretch across miniseries as streamlined as Sharp Objects and multiple seasons as inconsistent as Mr. Robot’s, with episodes ranging from 25 (Forever) to 90 minutes (Westworld, ugh). While some genres — like sci-fi (Maniac, Castle Rock, The OA) and the crime drama (True Detective, Big Little Lies, Bodyguard) — are a more intuitive fit for the form, it’s even spread into sitcoms (The Good Place), animated series (Gravity Falls), and family dramas (This Is Us).

Whatever your cultural tastes may be, there’s a puzzle-box series that suits them. (My stepdad, for example, loves Westworld, but was so unmoved by This Is Us that after one episode, he looked to the sky, shook his fists, and shouted, “Jesus Christ! Just kill the dad already!”) And their quality is as varied as their subject matter. The format doesn’t always live and die with the revelation of a Big Secret that only has significance within its own universe; many of the best examples of the form — The Good Place, Russian Doll, the revived iteration of Twin Peaks, The Leftovers — feature mysteries that are, at their core, about how to function as a person (or a robot) among other people in a real world that privileges individualism but requires interdependence.

The puzzle box isn’t a uniquely contemporary phenomenon. Viewers fixated on the identity of Laura Palmer’s murderer during the initial 1990-91 run of Twin Peaks; ratings tailed off immensely once the secret was revealed. Often held up as the quintessential puzzle box, Lost (2004-2010) inspired endless theorizing about what, exactly, the fuck was going on with that island. Both inspired a handful of knockoffs, but neither gave rise to anything one would describe as a trend — at least, nothing that compares to the current critical mass of mystery-centric television.

The core mystery of each puzzle box is what attracts attention, but the way each mystery unfolds — and concludes — is what keeps viewers, and therefore networks, invested. Puzzle boxes are, by design, a bottomless renewable energy source for the subreddit/Twitter THREAD (1/???)/media outlet explainer content economy. They generate infinite take possibilities, while also providing a built-in system for evaluating said takes beyond subjective agreement. It’s fun to share theories about what has happened and guesses about what will happen next; it revives the social component of television that wilted when appointment television was ruthlessly murdered by the DVR and streaming.

Yet while the revival of watercooler culture makes the puzzle box feel like a throwback, our departure from traditional viewing makes the format scalable in a way it wasn’t before. Whether a show airs week-to-week or drops season-by-season, networks increasingly operate from the idea that the binge-watch will be our primary mode of consumption. The assumption that autoplay guarantees at least a few hours of our attention has sparked a glut of shows with weird, bad pacing — but it also justifies packing episodes with intricate detail and narrative complexity that actually goes somewhere.

Committing to that approach is an effective strategy for standing out from the millions of other hours of TV available to audiences at any given moment. Current shows are not only competing for attention with their concurrently airing peers, but with long-deceased series that are available via streaming. A show can’t just be better than whatever’s airing the next channel over; it has to also be better than watching the season one of Real Housewives of Beverly Hills for the seventh time.

And what’s more satisfying than solving a puzzle or finding answers for our most pressing questions? There’s an extra layer of satisfaction when the answers are identical to the guesses you’ve made. Proving your theories lets you feel like a good, smart cultural consumer instead of someone who’s letting your brain atrophy in front of the Netflix “still watching?” screen. The puzzle box doesn’t just let the cachet of prestige television rub off on us; it makes us responsible for it, gives us the opportunity to feel like co-creators or, at the very least, respected critical thinkers. The process of solving the mystery isn’t just a quest for external validation, though — it’s an interactive, often social experience that minimizes the isolation of watching television for hours on end, and lets us assign order to a chaotic world.

However, not all conclusions are equally rewarding. Many puzzle box shows invest so much energy in the kind of complicated setups that attract obsessive viewer dissection that they lose sight of the fact that we expect them to deliver equally thrilling payoffs. Stakes can’t be raised infinitely, and that’s why Twin Peaks’s legacy of inevitably disappointing the part of its audience awaiting a smoking gun carried on through Lost, surviving today in Westworld and the weak sophomore seasons of Mr. Robot and True Detective. Even when series do manage to tie up every narrative thread neatly, their conclusions feel hollow if they fail to provide closure for the themes and characters that build a layer of emotional investment on top of our intellectual obsession. To some degree this is true for all television — and art, for that matter — but there’s something particularly insulting about following a mystery for years (or, these days, months) only for the creators to ultimately shrug.

Which is why these series are better when they try to grapple with mortality and morality and trauma rather than whether fuck-robots have consciousness or what fictional symbols mean. The best puzzle boxes aren’t the ones that make viewers feel smart for getting the right answers, or the ones that let us step into a world that has clear, logical, applicable rules, but the ones that encourage us to be okay with the ambiguous and unanswerable.

The Leftovers, for example, ended with Nora (Carrie Coon) giving her estranged husband Kevin (Justin Theroux) an explanation for the Sudden Departure, the rapture-like event that set the series in motion. In the end, the answer viewers wanted at the show’s beginning didn’t really matter that much. The question of what happened to those who disappeared became, over the course of three seasons, far less compelling than the question of how those who were left behind would cope with their losses. Nora’s account of visiting the other side may have been the truth; it may have been total bullshit. The ending wasn’t more or less satisfying either way. What’s important was that Kevin believed her, and his faith in her — irrational as it may be — let them both find peace.

The questions raised by human interdependence are irresolvable. Trying to understand them requires embracing a kind of emotional and intellectual lawlessness, and getting to practice that lawlessness by observing a contained fictional environment — in collaboration with other observers of that environment — gives us a low-stakes but satisfying opportunity to examine the weirdest, most vulnerable parts of our lived reality. There are mysteries you can solve, and those that keep you wondering forever.